The typical North American class 8 truck rear tandem axle is a full time 6×4 driveline with an inter-axle differential lock and optional wheel differential lock(s). This system offers good traction in most conditions, but suffers from spin loss and gear mesh inefficiencies. Alternate 6×2 drive-line systems can improve the spin loss and gear loss efficiency, but these systems are limited on tractive effort due to the single drive axle. The 6×2 system can utilize a wheel differential lock and to shift weight to the drive axle under low traction conditions to improve tractive effort, but cannot equal the performance of the 6×4 system traction. What is needed is a tandem axle system that has the efficiency of a 6×2 tandem with the tractive effort of the 6×4 system.